Rectilinear Figures — Chapter Summary
ICSE · Class 9 · Mathematics
Summary of Rectilinear Figures for ICSE Class 9 Mathematics. Part of the ICSE Class 9 Mathematics syllabus. Rectilinear means along a straight line.
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Overview
Rectilinear means along a straight line, in a straight line, or forming a straight line. A rectilinear figure is a plane figure bounded by straight lines. A polygon is a closed plane figure bounded by at least three line segments. The chapter builds the idea of polygons first, then studies their ang
Key Concepts
A polygon is a closed plane
A polygon is a closed plane figure bounded by at least three line segments. It is named by the number of sides, such as triangle, quadrilateral, penta
If each angle of a polygon
If each angle of a polygon is less than 180°, it is a convex polygon. If at least one angle is greater than 180°, it is a concave polygon. Unless othe
In a polygon of n sides
In a polygon of n sides, the sum of the interior angles is equal to (2n - 4) right angles. This rule works for regular and non-regular polygons, and i
If the sides of a polygon
If the sides of a polygon are produced in order, the sum of the exterior angles is 4 right angles, which is 360°.
If all the sides and all
If all the sides and all the angles of a polygon are equal, it is called a regular polygon. Each interior angle is (2n-4) rt. angles / n and each exte
Learning Objectives
- Identify rectilinear figures and polygons.
- Classify polygons by number of sides.
- Distinguish convex and concave polygons.
- Use the interior-angle and exterior-angle sum rules for polygons.
- Find unknown angles and number of sides in polygon problems.
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Content is aligned to the official syllabus. Refer to the board website for the latest curriculum.
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